Insulating device



1965 D. L. BURROWS 3,200,750

INSULATING DEVICE Filed March 15, 1962 FIG. I

FIG. 2

Dale L. Burrows, F|G 3 INVENTOR.

BY 4. %6Z.-

4.51 jaw w. SOLIQ United States Patent 3,20%,750 INSULATING DEVICE DaleL. liurrows, Huntsviile, Ala, assignor to the United States of Americaas represented by the Secretary of the Army Filed Mar. 15, 1962, Ser.No. 180,055 15 Claims. (Cl. 10292.5) (Granted under Title 35, US. Code(1952), see. 266) The invention described herein may be manufactured andused by or for the Government for governmental purposes without thepayment of any royalty thereon.

This invention relates broadly to missiles which travel at significantvelocities high in the atmosphere, and beyond the atmosphere, and moreparticularly to insulating the nose portion of the missile for thepurpose of rendering the surface resistant to high temperatures andthermal shocks encountered particularly upon re-entry to the atmosphere.

In the past a mixture of resin or some other ablative material andfibers has been coated on the nose portion of re-entry missiles in orderto protect the missile from extremely high temperature due to frictionduring reentry of the missile into the atmosphere. However certaindisadvantages are encountered when the mixture of fibers and an ablativematerial is used to protect the missile during reentry. For example,when the ablative material is heated a gas is generated causing bubblesand pits to form on the surface of the coating, these bubbles and pitspresent an uneven surface to the fluid flow over the nose portion of themissile during re-entry into the atmosphere and thus fail to provideuniform heat dissipation. Furthermore at the location of the bubbles andpits greater heat is generated due to the increase in friction. Theseproblems are overcome in the present invention by disposing a brush-likearrangement of fibers on a base which in turn is attached by somesuitable adhesive material to the nose portion of the missile.

In view of these facts, an object of this invention is to provide amissile having a nose portion that has a high resistance to heat.

Another object of this invention is to provide a missile having a noseportion which has high resistance to the stress of thermal shock.

A further object of this invention is to provide a missile having a noseportion which has uniform ablation characteristics.

A still further object of this invention is to provide insulation havingan appreciable reduction in weight for a required insulating value.

The invention will be more readily understood from the followingdescription taken in conjunction with the accompanying drawing, inwhich:

FIGURE 1 is a plan view of a missile with the insulation on its noseportion.

FIGURE 2 is a sectional view taken along line 2-2 of FIGURE 1 showingthe insulating material on the nose portion of the missile.

FIGURE 3 is an enlarged plan view of an insulating element showing thearrangement of some of the bristles on the element.

In the drawings, wherein for the purpose of illustration there is showna preferred embodiment of the in vention, in which the numeral 4designates a missile comprising a shell 6 and an insulated nose portion8.

The nose portion may be constructed in sections of structural platesteel or other suitable material shaped to the desired configuration.Attached to plate 6 by cement It) or some other suitable adhesivematerial is a plurality of base blocks 12 of ceramic material or resinbonded fibers; to the outside of which is attached by a bondingfiilififfifi Patented Aug. 17,1965

process or cement a brush-like coating of bristles 14. A refractoryinsert 1c is disposed on the foremost point of the nose since bristlesplaced at this point would tend to incline backwards during re-entry andexpose the missile shell to high temperatures. Furthermore the point ofgreatest aerodynamical heating is not at the stagnation point.

The bristle or fiber arrangement may be composed of fibers of differentmaterials or of fibers which are all of the same material. However, toobtain best results the fibers used should be selected from materialshaving both high aerodynamic heating insulator properties and highthermal conduction insulating properties. Preferred materials with theseproperties include fibrous, filamentary or bristle like materials ofsynthetic origin .and particularly those fabricated from ceramic andrefractory materials such as oxides of magnesium, silicon, thorium, andaluminum.

Along with the fibers of the above materials and intimately associatedwith them it is sometimes desirable to use fibers made from othermaterials having the follow ing properties: (1) good heat sink or heatabsorption qualities, (2) uniform endothermic decompositioncharacteristics and (3) high thermoconduction insulator properties and,in addition, having a decomposition temperature somewhat lower than thebase blocks referred to above, in order to derive the beneficialendothermic effects. However, it is not necessary that the bristles havea decomposition temperature lower than the blocks if the fibers are longenough so that the temperature drop through the fibers or bristles isgreat enough to prevent damage to the resin or ceramic blocks. Ingeneral, suitable materials having the above mentioned properties arefound among long chain resinous materials such as melamine, phenolicresins and nylons. Mixtures of fibers from both classes of the abovematerials may be varied when desired as may also the length of thefibers. In selecting the materials to be used and in determining thelength of the fibers, the heat protection requirements of the particulartrajectory under consideration would be the governing factor. Thus forsome trajectories an assortment of about ten percent of the resinousmaterial with the remainder-selected from one of the ceramic materialsmentioned would be suitable; As stated above fibers made from theceramic materials alone may be advantageous over a mixture of theceramic materials with the resinous materials because in the case ofcertain trajectories it may be desirable that the ablation shouldproceed smoothly without gasifying effects disturbing the surface flow,i.e. where low Reynolds number trajectories are contemplated it would beadvantageous to use the ceramic fibers having smooth ablationcharacteristics. Fibers having uniform ablation characteristics andhence producing a smoother external surface would induce a greater areaof laminar flow thus resulting in a much lower heat transfer than occurswhen a combination of the fibrous materials are used which generate amore turbulent flow.

The bristles or fibers although contacting each other would have anetwork of air cell between them (see magnified View in FIGURE 3) andinasmuch as the fibers are slanted to the surface a greater resistanceto heat transfer is provided than if the void were filled with a bondingagent such as resin. The major heat path would be down or along eachfiber and the inclination of the fibers from the normal wouldeffectively increase the heat path length and thus increase theinsulating value for a given thickness of the insulation material.

From an aerodynamic point of view the inclination of the fibers (asshown in FIGURE 2) would be beneficial inasmuch as the surface shearforces would tend to keep the bristles brushed back and hence maintainthe aerodynamic surface. The individual bristles are so fine that as faras the boundary layer is concerned the surface is essentially smooth.Such a surface may actually promote an increase of laminarfiow very muchin line with the phenomena occurring on the feathered surfaces of birds.Under the conditions of surface melting the surface hould becomesmoother and ablation would be a uniform process due to the homogeneousnature of the closely packed bristled surface. Inasmuch as each bristlei welded, fused or bonded to a base the whole insulating surface wouldactually withstand the aerodynamic forces (especially during theablating process) much better than a matted or stranded arrangement offibers impregnated with resin. Also the possible aerodynamicdisadvantage of bubbling or sputtering of resin will be avoided.

It is to be noted that the invention is not limited to bristles on aplurality of blocks cemented to a missile shell but the bristles couldhave their internal ends anchored on or in a common base which coversthe entire nose of the missile (with the exception of the solidrefractory insert at the foremost part of the nose).

. The following invention is claimed:

1. A heat resistant device comprising:

(a) a shell;

(b) means disposed on said shell for protecting said shell from hightemperatures,

() said means including a brush-like arrangement of fibers, and

(d) said brush-like arrangement of fibers being so oriented and so fineas far as a boundary layer is concerned that the surface thereof iessentially smooth to promote an increase of laminar flow very much inline with the phenomena occurring on the feathered surfaces of birds.

2. The device as set forth in claim ll wherein said fibers are ofablative material.

3. The device as set forth in claim 1 wherein said fibers are made ofmaterial having both high aerodynamic heating insulator properties andhigh thermal conduction insulating properties.

4. A missile comprising:

(a) a nose portion;

(b) an adhesive material disposed on said nose portion;

(c) a plurality of insulating elements attached to said adhesivematerial; and

(d) a brush-like arrangement of fibers disposed on each of saidinsulating elements.

5. The device as set forth in claim 4 wherein said fibers are ofablative material.

6. The device as set forth in claim 4 wherein said fibers and saidinsulating elements are made of material having both high aerodynamicheating insulator properties and high thermal conduction insulatingproperties.

7. A missile comprising:

(a) a nose portion;

i (b) an adhesive material disposed on said nose portion; (c) aplurality of insulating elements attached to said adhesive material; and(d) a brush-like arrangement of fibers tilted away from the front ofsaid nose portion and disposed on each of said insulating elements. 8. Amissile comprising: (a) a nose portion; (b) an adhesive materialdisposed on said nose portion; (c) a plurality of insulating elementsattached to said adhesive material; (d) a brush-like arrangement offibers disposed on each of said insulating elements; and (e) a solidrefractory insert mounted on the foremost part of said nose portion.

9. The device as set forth in claim 7 wherein said fibers are ofablative material.

10. The device as set forth in claim 7 wherein said fibers and saidinsulating elements are made of material having both high aerodynamicheat insulator properties and high thermal conduction insulatingproperties.

1.1. The device of claim 19 wherein a solid refractory insert is mountedon the foremost part of said nose portion.

12. A missile comprising: a nose portion having a relatively smooth andcontinuous. outer surface; a missile shell having an outer surface;means securing said nose portion to said shell so as to form acontinuous surface of said nose portion outer surface and said shellouter surface; and means secured to said relatively smooth andcontinuous outer surface of said nose portion for protecting said noseportion from high temperatures and including a brush-like arrangement offibers.

13. The device as set forth in claim 12 wherein said last mentionedmeans further includes an adhesive material disposed on said noseportion, a plurality of insulating elements attached to said adhesivematerial, and said brush-like arrangement of fibers being secured tosaid insulating elements. 7

14. The device as set forth in claim 12 wherein said fibers are tiltedaway from the front of said nose portion.

15. The device as set forth in claim 14 wherein a solid refractoryinsert is mounted on the foremost part of said nose portion.

References Cited by the Examiner UNITED STATES PATENTS 1/56 Nicholson1l7-l6 11/61 Parlanti 102-925 OTHER REFERENCES BENJAMIN A. BORCHELT,Primary Examiner.

ARTHUR M. HORTON, Examiner.

1. A HEAT RESISTANT DEVICE COMPRISING: (A) A SHELL; (B) MEANS DISPOSED ON SAID SHELL FOR PROTECTING SAID SHELL FROM HIGH TEMPERATURES, (C) SAID MEANS INCLUDING A BRUSH-LIKE ARRANGEMENT OF FIBERS, AND (D) SAID BRUSH-LIKE ARRANGEMENT OF FIBERS BEING SO ORIENTED AND SO FINE AS FAR AS A BOUNDARY LAYER IS CONCERNED THAT THE SURFACE THEREOF IS ESSENTIALLY SMOOTH TO PROMOTE AN INCREASE OF LAMINAR FLOW VERY MUCH IN LINE WITH THE PHENOMENA OCCURRING ON THE FEATHERED SURFACES OF BIRDS. 